In-situ post epitaxial treatment process

ABSTRACT

A process for forming an epitaxial layer on a semiconductor wafer substrate is provided. The process comprises providing a semiconductor wafer substrate and an area for forming an epitaxial layer on said semiconductor wafer substrate. The formation area consists essentially of an epitaxial layer process chamber. The semiconductor wafer substrate is introduced into the epitaxial layer process chamber and an epitaxial layer is formed on at least one surface of the semiconductor wafer substrate. Then, a chemical reagent is introduced into the epitaxial layer process chamber. The chemical reagent reacts with the epitaxial layer surface in situ to form an outer protective oxide layer.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.09/997,139, filed Nov. 28, 2001, now U.S. Pat. No. 6,471,771 which ishereby incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

This invention relates to a process for forming a protective oxide filmin-situ after deposition of an epitaxial silicon layer on a siliconsubstrate wafer.

Epitaxial deposition is a film grown over a crystalline substrate insuch a way that the atomic arrangement of the film bears a definedcrystallographic relationship to the atomic arrangement of the substratewafer. In the case of a monocrystalline substrate wafer, thecrystallographic orientation of the epitaxial layer will replicate thatof the substrate wafer wherein the substrate wafer provides thecrystallographic seed for epitaxial growth.

Commonly, growth of an epitaxial layer is accomplished by chemical vapordeposition (CVD) at temperatures well below the melting point of eitherthe substrate wafer or the film being deposited. In the CVD technique,the substrate wafer is heated in a chamber into which reactive andcarrier gases are introduced. For silicon deposition, reactive gasesinclude Silane (SiH₄), Dichlorosilane (SiH₂Cl₂), Trichlorosilane(SiHCl₃), and Silicon Tetrachloride (SiCl₄), with dopant gases thatinclude Arsine (AsH₃), Phosphine (PH₃), and Diborane (B₂H₆), and acarrier gas of hydrogen.

Epitaxial reactors are generally available in three basic designs. Thefirst design involves placing the substrate wafers on holders, calledsusceptors, in a horizontal position. Reactive and carrier gases arethen introduced into the growth chamber at one side, passed over thesubstrate wafers, and exhausted out the other side. The second designemploys a vertical system wherein the substrate wafers are placedhorizontally on a rotating susceptor, and the gases are introduced intothe chamber at the top, passed over the wafers, and exhausted out of thechamber at the bottom. Finally, the third design places the wafers nearvertically on a barrel-type rotatable susceptor, with the gasesintroduced in the top of the chamber, passed over the wafers, andexhausted out the bottom of the chamber. Older technology producedmultiple wafers simultaneously, and utilized each of these threedesigns. Newer technology, however, typically processes wafersindividually, and employs the first general design wherein the wafer isplaced horizontally on a rotating susceptor, and the gases areintroduced at one side of the chamber, passed over the wafer, andexhausted out the other side.

In each design, the susceptor is made of a nonreactive material capableof enduring extreme temperature and pressure variations, such asgraphite, and typically silicon carbide coated graphite. Heat istypically supplied by radio frequency (RF), ultraviolet (UV), infraredradiation (IR), or electrical resistance heaters, with processingtemperatures ranging from about 900° C. to 1200° C.

In general, epitaxial deposition begins by loading the substratewafer(s) onto the susceptor, and purging the ambient air out of thereaction chamber by supplying non-reactive gases such as helium, argon,or nitrogen, into the chamber. The temperature is then ramped up to thedesired level, and a mixture of the carrier gas and the reactive gases(including any desired dopant gas) is introduced into the chamber. Whenthe desired epitaxial layer thickness is achieved, non-reactive gasesare reintroduced into the chamber, and the temperature is ramped down.The wafer is then unloaded from the chamber.

If desired, an etching agent such as anhydrous hydrogen chloride (HCl)can be introduced before carrier and reactive gases are introduced. Thisetching agent will remove a thin layer off the surface of the substratewafer, as well as any contaminants adhered thereto. After such an etch,a contaminant free substrate surface with strong crystallographicstructure is provided for epitaxial deposition, and generally results ina higher quality epitaxial layer. This etching step can also be employedwithout the substrate wafer present, as a means of controlling epitaxialdeposition on the susceptor or other surfaces in the growth chamber.Additionally, prior to epitaxial deposition, a hydrogen bake can be usedto remove any native oxide growth on the surface of the wafer, bychemical reduction. This will provide a clean silicon surface on thesubstrate for epitaxial deposition.

In the case of a silicon epitaxial layer deposited on a siliconsubstrate wafer, the surface of the epitaxial layer is hydrophobic. Sucha hydrophobic layer is very reactive, and prone to attract contaminants.As such, it is common in the industry to employ a wafer cleaning andoxidizing step after the epitaxial deposition is complete. This cleaningand oxidizing is done to remove any contaminants that might have adheredto the epitaxial surface upon being removed from the deposition chamber,and to put a protective oxide layer, such as silicon dioxide (SiO₂) onthe surface of the epitaxial layer. An oxide layer surface ishydrophilic, which is much less reactive than a hydrophobic surface, andtherefore does not as readily attract contaminants. The oxide layer istherefore used to protect the surface of the wafer from contaminantsuntil the wafer is ready for further processing, wherein the oxide layeris removed and the silicon epitaxial layer is exposed and ready forprocessing.

This cleaning and oxidizing step adds both processing time and cost tothe production of the wafer and requires additional equipment andchemical usage. It is well known in the industry to use a wet chemicalbench to clean and oxidize the wafer surface. A typical cleaning andoxidizing process involving subjecting the wafer to submersion in twosequential solutions is as follows:

NH₄OH (29 weight %)+H₂O₂ (30%)+DI H₂O at 70-80° C.; and

HCl (37 weight %)+H₂O₂ (30%)+DI H₂O at 75-80° C.

Subjecting wafers so these solutions will slightly etch the surface ofthe wafer to remove contaminants, and then generate a thin oxide layer.This method of oxidizing is relatively uncontrolled however, and thethickness of the oxide layer is hard to control and predict.

SUMMARY OF THE INVENTION

The present invention relates to a process that overcomes thedisadvantages and problems set forth above. More specifically, a processis provided for growing an outer protective layer on the outer surfaceof a semiconductor wafer directly in an epitaxial reactor chamberimmediately after epitaxial deposition. The subject process involves thegrowing of protective films in reactors designed explicitly for thedeposition of epitaxial silicon films. The growth of these protectivefilms is accomplished during typically an unproductive part of thedeposition cycle, namely, the cool-down phase. In any case, theoxidation occurs before the wafer is removed from the epitaxialdeposition equipment.

By incorporating the novel process technique of the present inventioninto the epitaxial reaction sequence, the elimination of the costly andtime-consuming cleaning and oxidizing step will result. Further, sincethe oxidation occurs in the epitaxial equipment, the process can be muchmore tightly controlled, and will result in a higher quality oxide.

Additionally, by incorporating the process of the present invention, theapplication of an outer layer on the epitaxial silicon is not limited toan oxide, but could also include nitrides, or other beneficial layers.Nitride layers cannot currently be achieved through any presentlyavailable wet treatment technique.

These features are believed to be a novel approach utilizing existingepitaxial deposition equipment, and applying a new method. The inventiondiscloses a method that will allow for the elimination of post-epitaxialwet processing for cleaning and oxidizing in preparation for waferstorage. More specifically, the method comprises introducing amonocrystalline substrate wafer into epitaxial equipment, processing thewafer to form an epitaxial layer on the surface of the substrate waferand having the same crystalline properties as the substrate wafer, andthen forming a protective layer on the surface of the epitaxial layerbefore removing the wafer from the epitaxial equipment.

The semiconductor wafer substrate is introduced into the epitaxial layerprocess chamber, and the temperature in the epitaxial layer processchamber is increased to a predetermined operating temperature. Typicaloperating temperature during epitaxial deposition ranges from about1025° C. up to about 1150° C., and preferably from about 1050° C. to1100° C. Typical operating pressure is about 760 Torr for atmosphericdeposition, but can go down to about 1 Torr for low pressureapplicatons. Upon achieving the desired temperature, appropriatereactive and carrier gases are introduced into the epitaxial depositionchamber to facilitate layer growth. The operating temperature ismaintained for a time sufficient to facilitate epitaxial layer growth ofa layer up to 15 microns thick, preferably in the range of 2 to 4microns thick. Upon achieving the desired layer thickness, the reactivegas supply is terminated, and the deposition chamber is purged withnon-reactive gas. As previously described, the epitaxial layer ishydrophobic in nature, is of uniform thickness, and has the samecrystallographic orientation as that of the substrate wafer.

The temperature of the deposition chamber is then ramped down to adesired unload temperature. While ramping down the temperature, achemical reagent gas is introduced into the epitaxial depositionchamber. Preferably, the step of introducing the reagent gas into thedeposition chamber occurs immediately after purge gas is introduced intothe chamber. In another preferred embodiment, the operating temperatureis ramped down to a predetermined reduced temperature beforeintroduction of the reagent gas.

When the reagent gas is introduced into the deposition chamber, thereagent gas reacts in-situ with the hydrophobic epitaxial layer surfaceto form an outer layer that is substantially hydrophilic. In onepreferred step the substantially hydrophilic outer layer surface is anin-situ oxidation step. In another preferred step the substantiallyhydrophilic outer layer surface is an in-situ nitridation step. Thereaction between the reagent gas and the hydrophobic epitaxial layer ispreferably conducted without any additional heat being added to thedeposition chamber, but rather takes advantage of the heat present fromthe epitaxial deposition during the temperature reduction step. Yetanother additional process step preferably includes the step ofsubsequently depositing in-situ at least one additional layer onto thesubstantially hydrophilic outer layer.

In any case, it is preferred that the step of reacting the reagent gaswith the hydrophobic epitaxial layer to form the hydrophilic layer isconducted without requiring substantial additional process time comparedto the epitaxial deposition process described above.

In an alternate embodiment, a stabilized heat controlled process couldbe added to the epitaxial deposition process specifically added tosupport the formation of the protective hydrophilic layer. In this case,the process time required for processing in the epitaxial equipment isslightly increased, such as for an additional 20 seconds of controlledheating. By controlling the temperature during formation of thehydrophilic layer, more precise control of the layer thickness anduniformity can be achieved. Again, the formation of the hydrophiliclayer is accomplished in-situ after deposition of the epitaxial layer,and before the wafer is removed from the epitaxial equipment.

The foregoing and other objects, features and advantages of theinvention will become more readily apparent from the following detaileddescription of a preferred embodiment that proceeds with reference tothe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a conventional cylindrical orbarrel type-batch epitaxial reactor.

FIG. 2 is a schematic sectional view of a conventional single waferepitaxial process chamber wherein deposition of an epitaxial layeroccurs in deposition equipment know as an “ASM Reactor”.

FIG. 3 is a top view of the conventional single wafer epitaxial processchamber of FIG. 2.

FIG. 4 is a schematic sectional view of a single wafer epitaxial processchamber wherein deposition of an epitaxial layer.occurs in depositionequipment known as a “Centura Reactor”.

FIG. 5 is a schematic depiction of the process of epitaxial depositionrelated to equipment used in FIG. 1.

FIG. 6 is a schematic depiction of the process of epitaxial depositionrelated to equipment used in FIG. 2.

FIG. 7 is a schematic depiction of the process of epitaxial depositionrelated to equipment used in FIG. 3.

FIG. 8 is a schematic depiction of a “Centura Reactor”.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a typical cylindrical or barrel type batch epitaxialreactor (1), in which a polyhedral susceptor (3) is inserted within abell jar (2). The susceptor can be rotated via a rotational shaft (5).The susceptor (3) contains individual facets (9) that include recessedpockets (7) which can accommodate semiconductor wafers (not shown)within each pocket (7). There can be one pocket (7) or a multitudethereof, depending on the wafer diameter to be processed. The bell jar(2) is surrounded by a quartz lamp heater (11) and a reflective heatshield (13) which is designed to heat the susceptor (3) and the wafers(not shown) through the wail of the bell jar (2) by reflecting incidentenergy back toward the susceptor (3). The entity is hermetically sealedwith a top plate (17) and process gases (10) are introduced into thereaction chamber via the gas inlets (15).

Once the process gases (10) have reacted with the wafers, any remainingprocess gases (10) and any byproducts (23) which may be produced, areflushed out through the exhaust opening (19). The space defined by theheat shield (13) and the outer wall (14) usually houses a coolingmechanism, such as a cooling gas and/or water pipes (not shown).

A typical single wafer epitaxial reactor chamber (30) is shown in FIG.2. In this type of epitaxial reactor, a generally plate-shaped susceptor(53) is mounted on a chuck (51), which is in turn supported and rotatedby a rotary shaft (57). The rotary shaft (57) extends through a coupling(59), which allows for rotation and vertical adjustment. The susceptor(53) is enclosed by a top panel (31), a bottom panel (33), a verticalwall section (35), and a lower chamber bottom panel (37). Two sidepanels (not shown) complete the enclosure of the unit such that thesusceptor (53) is completely enclosed. Top panel (31), bottom panel(33), and the two side panels (not shown) mate with a gas injector (41)at injector flange (39), and mate with a gas outlet (49) at outletflange (45).

A wafer (55) is removably positioned onto the susceptor (53), andvertically adjusted to be in the optimal position for gases to flow overthe wafer (55). The wafer (55) is heated by quartz lamps (not shown) ora quartz lamp arrangement that is placed on the top, on the bottom, oron both sides of the reaction chamber. As shown in FIG. 3, the processgases are introduced with established gas flow and velocity, asindicated by the arrow (43). The process gases will flow across thewafer (55), proceed to the rear portion (47) of the reaction chamber,and exit through the gas outlet (49). The process gases are similar tothose described for the cylindrical type batch reactor.

Another type of single wafer epitaxial reactor is shown in FIG. 8. Thistype is marketed by Applied Materials Corporation and is commonly knownas the “Centura Reactor”. The reactor (110) contains one or more loadingchambers (112) where wafer carriers (not shown) are placed. An automatedwafer handler (114), located within a transfer chamber (116), is used totransport individual wafers from a loading chamber (112) to a singlewafer reactor (118), then to a cooling chamber (120) before returningthe wafer to the wafer carrier in the loading chamber (112). The reactor(110) can contain as many as 8 attachable and/or detachable componentloading chambers (112), single wafer reactors (118), and coolingchambers (120), in any combination desired, with the stipulation of amaximum of three high temperature single wafer reactors (118). Eachcomponent is serviced by the automated wafer handler (114). The loadingchambers (112) have doors (not shown) between the ambient area outsidethe epitaxial equipment and transfer chamber (116), such that when thedoor to the ambient area is open, the door to the transfer chamber (116)is closed with an airtight seal. Similarly, when the door to thetransfer chamber (116) is open, the door to the ambient area is closedwith an airtight seal. These seals help prevent contamination in theambient area from entering the area within the equipment itself.

FIG. 4 reveals the single wafer reactor (70) in which layers of siliconcan be deposited onto a wafer (81). The reactor has a top wall (73),side walls (75) and a bottom wall (78) that encloses the reactionchamber (68) into which the wafer (81) can be positioned. The wafer (81)is removably mounted on susceptor (82) which is then mounted on apedestal (84) that is rotated by a motor (86) to provide a homogeneouslyaveraged environment for the wafer (81). The wafer (81) is heated by alight source from high intensity lamps (88) and (91). The top wall (73)and the bottom wall (78) are highly transparent to light energy in orderto enable the energy from lamps (88) and (91) to enter the reactionchamber (68). An excellent material choice for the top and bottom walls(73) and (78) is quartz because it is transparent to light at visible IR(infrared) and UV (ultra violet) frequencies. It also has a sufficientlyhigh strength to support pressure differences between the outside andthe reaction chamber (68), and it has a low rate of outgasing andcontamination.

Process gases flow from a gas input port (100) and across the wafer (81)to an exhaust port (102). The gas input port (100) is connected to gasmanifolds (not shown) that provides one or a mixture of gases to enterthrough pipes (not shown) into the input port (100). Gas concentrations,gas flow rates, substrate rotation and temperatures are selected in away so that processing uniformity is optimized. Rotation of the wafer(81) and thermal gradients from lamps (88) and (91) can have asignificant influence of gas flow profiles in the reaction chamber (68).The main flow profile, however, is dominated by the laminar flow fromthe gas input port (100), across the wafer (81) to the exhaust port(102). Pressures are maintained typically between 1 Torr to 760 Torr,depending on specifications and applications. Since these are elevatedpressures as compared to the LPCVD (low pressure chemical vapordeposition) process pressures of less than 1 Torr, such a process isalso referred to as high pressure CVD (chemical vapor deposition) orAPCVD (atmospheric pressure chemical vapor deposition).

Processing wafers in any of the epitaxial reactors explained above willprovide an epitaxial silicon layer on the surface of the wafer, with theorientation of the layer being the same as that of the wafer, andcharacteristics of the epitaxial layer such as resistivity controlled bythe process gases. It is possible to then grow an in-situ protectivefilm layer in the same reaction chamber in which the epitaxial films aregrown. As such, subsequent wet processing to provide such a protectivefilm layer can be omitted. Therefore, a preferred embodiment of theinvention is an oxidation step immediately after epitaxial deposition togenerate a protective film layer with a hydrophilic surface. Thethickness of the protective film layer of the present invention isexpected to be in the range of 10 Å to 50 Å.

Another preferred embodiment of the proposed invention is an oxidationstep to provide a thin oxide layer of about 10 Å to 50 Å during thecool-down phase of the process without requiring added process time. Ithas been determined that the cool down temperatures and times aresufficient to achieve such a thin film formation. In the case of theCentura reactor, this oxide growth could be facilitated in any areawithin the equipment.

Another preferred embodiment encompasses a reduction in wet processing.An oxidizing bath after epitaxial deposition would not be required. Anyof the thin oxide films formed by the subject process can easily beremoved via a hydrofluoric acid (HF) etch, should the user need a baresilicon surface during subsequent semiconductor wafer processing.

In a further embodiment, one or more reaction chambers can be added tothe AMT Centura reactor described in FIGS. 4 and 5 to perform anycombinations of subsequent processes, including, but not limited tooxidation, nitridation, CVD backside deposition, plasma etching, etc. Insuch a case, the material would receive epitaxial deposition in onechamber, and be moved to another chamber to receive the protective film,without leaving the confines of the environmentally controlled reactor.

Another embodiment is the possibility of using the thin film formed,such as the thin oxide film as a seed for subsequent treatment (such asoxidation or the like) by wafer users. For example, sandwich structurescan be formed such as a nitride film on top of an oxidation as a firstdevice-processing step.

Depending on the epitaxial reactor type, and the individual epitaxialwafer specification, numerous recipes are possible. A common cycle foreach of the previously mentioned reactor types presently used is shownin FIGS. 5-7. It should be noted that in all three examples a chemicalreagent is introduced into the epitaxial layer process chamber (afterformation of an epitaxial layer), and the chemical reagent reacts withthe epitaxial layer (which is hydrophobic) in-situ to form an outerlayer which is substantially hydrophilic. More specifically, anoxidation or nitridation of the epitaxial layer takes place during thecooling phase of the process without adding time to the process sequenceprior to unloading the wafer(s) from the reactor chamber. FIGS. 5-7represent the processes in scale to each other for the main threedifferent types of equipment used for this type of epitaxial deposition.The Applied Materials batch type barrel reactor is represented by therecipe of FIG. 5, the ASM single wafer reactor by the recipe shown inFIG. 6, and the single/multiple single wafer chamber Applied Materials(Centura) reactor by the recipe depicted in FIG. 7. All three figuresshow the process cycle with regard to the process temperature, indicatedon the ordinate in ° C., and the time t in minutes on the abscissa towhich the cycle is associated. It should be understood that all theseprocess steps are generalized.

A typical operation sequence for the conventional barrel type batchreactor process (200), which is illustrated in FIG. 5, is as follows:

(a) Ramp-up (206) at 0.7° C./s to 1150° C. in an inert H₂ atmosphere.

(b) Bake/etch (209) for about 5 minutes in H₂ and HCl at a temperatureof 1150° C.

(c) Ramp-down (212) at 0.5° C./s to a temperature of 1130° C.

(d) Epitaxial deposition (215) in H₂ employing a reactive gas forsilicon epitaxial deposition such as Trichlorosilane (SiHCl₃) and adopant such as Phosphine for time period of about 9 minutes.

(e) Ramp-down (218) at 0.5° C./s in O₂ and H₂ for forming thinoxidation.

(f) Unload the finished wafer at about 300° C.

A typical operation sequence for the single-wafer reactor process (300),which is illustrated in FIG. 6, is as follows:

(a) Ramp-up (306) at 3.2° C./s to a temperature of 1190° C. in an inertH₂ atmosphere

(b) Bake/etch (309) for approximately 2.5 minutes in H₂ and HCl attemperature 1190° C.

(c) Ramp-down (312) at 6° C./s to a temperature 1150° C.

(d) Epitaxial deposition (315) in H₂, employing a reactive gas forsilicon epitaxial deposition such as Trichlorosilane (SiHCl₃) and adopant such as Phosphine.

(e) Ramp-down (317) at 6° C./s in O₂ and H₂ for forming thin filmoxidation.

(f) Unload the finished wafer at about 900° C.

A typical operation sequence for the Centura reactor process (400),which is illustrated in FIG. 7, is as follows:

(a) Ramp-up (406) at 18° C./s to a temperature of 1130° C. in an inertH₂ atmosphere.

(b) Bake (409) for approximately 1 min. in H₂ at 1130° C.

(c) Epitaxial deposition (412) in H₂, employing a reactive gas forsilicon epitaxial deposition such as Trichlorosilane (SiHCl₃) and adopant such as Phosphine for time period from about 15 seconds through 4minutes, depending on desired layer thickness.

(d) Ramp-down (415) at 18° C./s in O₂ and H₂ for forming thin filmoxidation.

(e) Unload the finished wafer at about 700° C.

Some care has to be taken when dealing with an atmosphere consisting ofoxygen (O₂) and hydrogen (H₂) due to the possibility of explosivemixture formation. The limit to form a dangerous mixture of hydrogen andoxygen is reached at about 4.65 volume % of H₂ in pure O₂ at roomtemperature or, respectively, a 6.1 volume % of O₂ in pure H₂ underatmospheric pressure (760 Torr). These ratios will obviously changeunder different temperature and pressure conditions.

Batch epitaxial reactors typically cool down from the depositiontemperature of 1150° C. to about 300° C. to 400° C. (at 760 Torr) beforeunloading the wafers. Reactors with one or more single wafer reactionchambers typically cool from 1100° C. to about 700° C. to 900° C. (at760 Torr). Reactors with single or multiple single wafer reactionchambers can afford higher chamber unload temperatures because theytypically contain cool down areas or chambers in which the wafers cancool down to temperatures which are tolerated by the wafer carriers, andautomated wafer handlers can handle elevated temperatures. These cooldown areas are still contained within the controlled environment of theepitaxial equipment, and therefore do not expose the wafer to potentialcontaminants associated with ambient air.

An inert gas, such as helium or argon could be mixed into the oxygensource to modify dangerous levels of hydrogen-oxygen ratios. The gaseswould then be fed through mass flow controllers (MFC), mixed withprocess gases (hydrogen in this case) and fed into the deposit manifold.Additional safety valves and leak detectors coupled with automaticshut-off mechanisms would render additional safety features. Anotherpossible solution is to elect the ideal safe gas ratio by taking thelower explosive mixture and divide it by a safety factor such as 10 to100.

EXAMPLES Example 1

A single wafer reactor was utilized to deposit an epitaxial layer on awafer at a temperature of 1130° C. SiHCl₃ was used as the reactive gaswith H₂ as the carrier gas. When the desired thickness of the epitaxiallayer was achieved, the reactive gas supply was terminated, and thereactor was purged with H₂ gas at 60 liters per minute prior to cooldown for 10 seconds. At the beginning of the cool down cycle, a mixtureof between 1000 and 2000 ppm O₂ in Argon was introduced at 5 liters perminute while maintaining the 60 liters per minute of H₂ gas flow, for 30seconds. During this 30 second time period, the temperature was reducedto 900° C. and stabilized. Wafers measured demonstrated a hydrophobicoxide layer with a thickness layer of 8 Å, having good oxide thicknessuniformity, good haze levels, and good particle levels.

Example 2

A single wafer reactor was utilized to deposit an epitaxial layer on awafer at a temperature of 1130° C. SiHCl₃ was used as the reactive gaswith H₂ as the carrier gas. When the desired thickness of the epitaxiallayer was achieved, the reactive gas supply was terminated, and thereactor was purged with H₂ gas at 60 liters per minute prior to cooldown for 30 seconds. At the beginning of the cool down cycle, a mixtureof between 1000 and 2000 ppm O₂ in Argon was introduced at 5 liters perminute while maintaining the 60 liters per minute of H₂ gas flow, for 30seconds. During this 30 second time period, the temperature was reducedto 900° C. and stabilized. Wafers measured demonstrated a hydrophobicoxide layer with a thickness layer of 8 Å, having good oxide thicknessuniformity, good haze levels, and good particle levels.

Example 3

A single wafer reactor was utilized to deposit an epitaxial layer on awafer at a temperature of 1100° C. SiHCl₃ was used as the reactive gaswith H₂ as the carrier gas was employed. When the desired thickness ofthe epitaxial layer was achieved, the reactive gas supply wasterminated, and the reactor was purged with H₂ gas at 60 liters perminute prior to cool down for 10 seconds. While maintaining the H2 gasflow, the temperature was cooled to a temperature of 1000° C., whereinthis temperature was maintained during the oxidation stage. A gasmixture of between 1000 and 2000 ppm O₂ in Argon at 5 liters per minutewas introduced into the reactor, with H₂ gas flow at 60 liters perminute. The oxide deposition stage was allowed to run for 7 seconds inthis constant temperature and gas, after which the O₂/Ar mixture wasterminated, and the ramp down stage continued. Wafers measureddemonstrated a hydrophobic oxide layer with a thickness layer of 10 Å,having good thickness uniformity, good haze levels, and good particlelevels.

It is obvious that a skilled artisan could easily adjust variousparameters such as time exposed to the O₂/Argon gas mixture, thetemperature of exposure, or even the concentration of O₂ in argon toobtain a desired oxide thickness layer, for example of up to 15 Å, ormore.

Having illustrated and described the principles of my invention in apreferred embodiment thereof, it should be readily apparent to thoseskilled in the art that the invention can be modified in arrangement anddetail without departing from such principles. I claim all modificationscoming within the spirit and scope of the accompanying claims.

That which is claimed is:
 1. A method of forming a protective oxide layer on the surface of an epitaxial layer, comprising: placing a substrate wafer in an epitaxial reactor; depositing an epitaxial layer on at least one surface of the substrate wafer; subjecting the substrate wafer containing the epitaxial layer to a gas mixture containing oxygen to grow an oxide layer; and removing the substrate wafer from the epitaxial reactor.
 2. The method according to claim 1, wherein the gas mixture containing oxygen contains an amount of oxygen below the lower explosive mixture level.
 3. The method according to claim 1, wherein the gas mixture containing oxygen also contains an inert gas.
 4. The method according to claim 3, wherein the gas mixture containing oxygen has an oxygen concentration of less than about 2000 parts per million.
 5. The method according to claim 3, wherein the inert gas is Argon.
 6. The method according to claim 3, wherein the inert gas is helium.
 7. The method of claim 1, wherein the protective oxide layer thickness is about 15 angstroms or less.
 8. A method of forming a protective oxide layer on the surface of an epitaxial layer, comprising: placing a substrate wafer in an epitaxial reactor; depositing an epitaxial layer on at least one surface of the substrate wafer; subjecting the substrate wafer to hydrogen gas; subjecting the substrate wafer to a gas mixture containing oxygen to grow an oxide layer; and removing the substrate wafer from the epitaxial reactor.
 9. The method according to claim 8, wherein while the substrate wafer is being subjected to the hydrogen gas, the wafer is also subjected to the gas mixture containing oxygen.
 10. The method according to claim 9, wherein the substrate wafer is subjected to the gas mixture containing oxygen for less time than the substrate wafer is subjected to the hydrogen gas.
 11. The method according to claim 10, wherein the substrate wafer is subjected to the gas mixture containing oxygen for less than one minute. 